JP2009083171A - Droplet discharge head and droplet discharge apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose a structure of electrostatic actuator corresponding to the movement of the ink in a pressure chamber. <P>SOLUTION: A liquid droplet ejection head is equipped with a nozzle substrate 4 having a nozzle 8, a cavity substrate 2 which has the pressure chamber 13 formed in an oscillating board 12 of oblong configuration whose bottom face can be deformed by an electrostatic force and in which one end side of the longitudinal direction of the pressure chamber 13 communicates to the nozzle 8 of the nozzle substrate 4 while the other end side of the longitudinal direction communicating to a reservoir 14 for storing an ejected liquid, and an electrode substrate 3 having an individual electrode 18 which is arranged opposite to the oscillating board 12 through a clearance. The clearance between the oscillating board 12 and the individual electrode 18 gets larger in sequence in the direction toward the center in each clearance between the intermediate part and both ends in the longitudinal direction of the pressure chamber 13. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a droplet discharge head such as an inkjet head, and a droplet discharge apparatus including the droplet discharge head.

  In an electrostatic drive type ink jet head, a plurality of grooves are generally formed in an electrode substrate made of glass or the like, and independent individual electrodes (also referred to as counter electrodes because they are electrodes facing a vibration plate described later) inside the grooves. ), And the individual electrodes are opposed to the diaphragm constituting the bottom surface of the ink pressure chamber through a gap. Then, an electrostatic force is generated by applying a voltage between the diaphragm and the individual electrode, and the diaphragm is sucked and bent toward the individual electrode, and ink is ejected from the nozzle using the pressure change caused by the deformation of the diaphragm. Discharge from.

  In an ink jet printer using an ink jet head to which the above parallel plate type electrostatic actuator is applied, it is required to realize efficient driving and increase the volume of ink droplets at a low voltage. Therefore, conventionally, a device for obtaining a larger displacement of the diaphragm at a lower voltage has been proposed by configuring the gap between the diaphragm and the individual electrode constituting the electrostatic actuator to be non-parallel.

For example, a configuration in which drive electrodes corresponding to individual electrodes are configured in a stepped manner in the width (short side) direction of the diaphragm is disclosed (for example, Patent Document 1). In addition, there is disclosed a configuration in which individual electrodes are formed in a step shape in the length (long side) direction of the diaphragm, and the shallowest portion immediately below the nozzle portion is disclosed (for example, Patent Document 2). Also disclosed is one in which the central portion of the diaphragm is shallowest in the width direction of the diaphragm (for example, Patent Document 3). Further, a configuration is also disclosed in which the central portion of the diaphragm is deepest in the length direction of the diaphragm and the behavior of the diaphragm at the stepped portion is continuous (for example, Patent Documents). 4).
Japanese Patent Laid-Open No. 11-291482 JP 2000-318155 A JP 2001-287359 A JP 2006-289944 A

  In order to drive the diaphragm more efficiently and increase the speed, it is necessary to drive the diaphragm in accordance with the behavior of the ink. However, with the technique shown in the above-described conventional example, it is difficult to match the behavior of the vibration plate on the bottom surface of the ink pressure chamber constituting the electrostatic actuator with the behavior of the ink in the ink pressure chamber to be driven. It has a structure. That is, in the conventional inkjet head, in order to efficiently perform the behavior of the electrostatic actuator, there has been no structural proposal of an actuator for driving the diaphragm in accordance with the movement of the ink in the ink pressure chamber. It was.

  The present invention has been made in view of the above problems, and adapts to the movement of ink in the pressure chamber when the diaphragm on the bottom surface of the pressure chamber constituting the electrostatic actuator for discharging droplets is sucked to the opposing electrode. It is an object of the present invention to propose a new structure of an electrostatic actuator, and to provide a droplet discharge head having an electrostatic actuator capable of driving a diaphragm at high speed, and a droplet discharge apparatus including the droplet discharge head.

The droplet discharge head of the present invention has a nozzle substrate having a nozzle and a pressure chamber formed on a horizontally long diaphragm whose bottom surface can be deformed by an electrostatic force, and one end side in the longitudinal direction of the pressure chamber is a nozzle. A cavity substrate that communicates with the nozzle of the substrate, and that the other end in the longitudinal direction communicates with a reservoir that stores discharge liquid, and an electrode substrate that has an individual electrode, and the individual electrode is disposed opposite to the diaphragm with a gap. The gap between the diaphragm and the individual electrode is gradually increased toward the central portion between the intermediate portion and both end portions in the longitudinal direction of the pressure chamber.
With this configuration, the diaphragm can be simultaneously brought into contact with the individual electrode from both the nozzle communication side and the reservoir communication side, and the discharged liquid can be quickly and simultaneously sucked into the pressure chamber from both sides. As a result, the diaphragm can be quickly sucked to the individual electrode side in accordance with the movement of the discharge liquid in the pressure chamber, and the diaphragm can be driven efficiently and at high speed.
In addition, since the load when the diaphragm is brought into contact with the individual electrode can be reduced and the diaphragm can be quickly sucked into the individual electrode, the drive voltage can be reduced and the response from the nozzle can be reduced without impairing the response. By increasing the amount of discharged liquid, the discharge capacity of the head can be improved and the operation speed can be increased.

The droplet discharge head has a gap width in a portion corresponding to a position where the inertance of the discharge liquid in the pressure chamber is equal between the nozzle communication side and the reservoir communication side of the pressure chamber in the gap between the individual electrode and the diaphragm. , And the gap width at both end portions in the longitudinal direction of the pressure chamber is the narrowest.
By doing so, since the behavior of the ink in the pressure chamber matches the change of the diaphragm, the diaphragm can be sucked to the individual electrode side most efficiently.
When the horizontally elongated pressure chamber is substantially symmetrical in the left and right direction in the longitudinal direction, the gap width at the intermediate portion in the longitudinal direction of the pressure chamber and the gap width at both end portions in the longitudinal direction of the pressure chamber are minimized. Is preferred.

  Further, the maximum distance of the gap between the longitudinal intermediate portion of the pressure chamber and the longitudinal end portion on the nozzle communication side is larger than the maximum distance of the gap between the intermediate portion and the longitudinal end portion on the reservoir communication side. It is preferable to make it large. This is because the amount of deformation of the diaphragm on the nozzle side of the pressure chamber can be made large so that it becomes easier to perform drive control in accordance with the ink meniscus drawing of the nozzle portion.

Moreover, it is preferable that the individual electrodes of the electrode substrate have a stepped shape corresponding to the gap. It is easy to form the individual electrode forming grooves of the electrode substrate in a stepped manner by repeating etching, and the electrode substrate constituting the electrostatic actuator can be easily formed only by forming an electrode material on the groove surface. Because. In addition, there is an effect that a gap with a predetermined interval can be formed by simply joining the electrode substrate to the cavity substrate.
In addition, it is preferable that the stepped adjacent steps of the individual electrodes are gradually reduced toward the central portion between the intermediate portion and both end portions in the longitudinal direction of the pressure chamber. According to this, since the diaphragm can continuously and smoothly contact from the middle part and both ends in the longitudinal direction of the pressure chamber toward the center part between them, the control of the amount of liquid discharged from the nozzle can be controlled. This is because it becomes easy.

  The droplet discharge device of the present invention is provided with any one of the above-described droplet discharge heads in the droplet discharge portion, and therefore, the effects described with respect to the droplet discharge head can be achieved.

Embodiment 1
FIG. 1 is an exploded perspective view showing an ink jet head which is a liquid droplet ejection head according to Embodiment 1 of the present invention, and FIG. 2 is a longitudinal sectional view of the ink jet head of FIG. The ink jet head 1 of this example is configured by laminating a cavity substrate 2, an electrode substrate 3, and a nozzle substrate 4.

  The nozzle substrate 4 is made of silicon or the like. For example, a cylindrical first nozzle hole 6 communicates with the first nozzle hole 6 and has a cylindrical second nozzle hole having a diameter larger than that of the first nozzle hole 6. A plurality of nozzles 8 having 7 are formed. The first nozzle hole 6 is formed so as to open on the ink discharge surface (the surface opposite to the bonding surface with the cavity substrate 2), and the second nozzle hole 7 opens on the bonding surface with the cavity substrate 2. It is formed to do.

  The cavity substrate 2 is made of, for example, single crystal silicon, and has a plurality of laterally long groove-like recesses that serve as pressure chambers 13 (also referred to as ink pressure chambers or ink discharge chambers in order to discharge ink). The bottom wall, which is one of the wall surfaces constituting the pressure chamber 13, has a horizontally long shape (usually rectangular) corresponding to the recess, and is formed as a flexible diaphragm 12 that can be deformed by an electrostatic force. . The cavity substrate 2 is formed with one recess serving as a reservoir 14 for supplying ink to each pressure chamber 13. An end 15 in the longitudinal direction of the pressure chamber 13 communicates with the nozzle 8 of the nozzle substrate 4, and an orifice 15 that communicates with a reservoir 14 that stores ink for ejection is formed on the other end in the longitudinal direction. The reservoir 14 is formed with an ink supply port 17A for supplying ink thereto.

  An insulating film (not shown) made of silicon oxide, aluminum oxide or the like is formed on the surface of the cavity substrate 2 to which the electrode substrate 3 is bonded. This insulating film is for preventing dielectric breakdown and short-circuiting when the inkjet head 1 is driven. Further, on the surface of the cavity substrate 2 on the side to which the nozzle substrate 4 is bonded, a droplet-resistant protective film (not shown) made of silicon oxide or the like is formed. This anti-droplet protective film is for preventing the cavity substrate 2 from being etched by the discharge liquid inside the pressure chamber 13 and the reservoir 14.

The electrode substrate 3 is made of, for example, borosilicate glass, and individual electrodes 18 that are independent electrodes are formed in a plurality of horizontally long electrode forming grooves 19. The electrode substrate 3 is bonded to the cavity substrate 2 in a state where the individual electrode 18 is opposed to the diaphragm 12 of the cavity substrate 2 with a gap 20 therebetween. The diaphragm 12 and the individual electrode 18 constitute an electrostatic actuator of the inkjet head 1.
As shown in FIG. 2, the gap 20 between the diaphragm 12 and the individual electrode 18 is between the intermediate portion and each end portion between the intermediate portion in the longitudinal direction of the pressure chamber 13 and both end portions thereof. It gets wider as you go to the center of the city.

  The electrode substrate 3 further has an ink supply port 17B that communicates with the ink supply port 17A of the cavity substrate 2. The ink supply port 17B is provided to supply the reservoir 14 with ink as a discharge liquid from the outside. The gap 20 formed between the cavity substrate 2 and the electrode substrate 3 is sealed with a sealing material 22 in order to prevent water vapor and the like from entering there.

  Next, the operation of the inkjet head 1 will be described. As shown in FIG. 2, a drive circuit 25 is connected to the common electrode terminal 21 of the cavity substrate 2 and the electrode terminal portion 18 </ b> A of the individual electrode 18. When a pulse voltage is applied between the diaphragm 12 of the cavity substrate 2 and the individual electrode 18 by the drive circuit 25, an electrostatic force (Coulomb force) is generated between them, as shown in FIG. 12 is attracted to the individual electrode 18 side and deformed, and most of it is brought into contact with the individual electrode 18. The contact of the diaphragm 12 with the individual electrode 18 begins to occur from both ends and the middle of the diaphragm 12 with a narrow gap 20 between them, and in the longitudinal direction of the diaphragm 12 with a wide gap 20. It progresses sequentially toward the central portion between the both end portions and the intermediate portion, and finally, the central portion having the widest gap 20 contacts. In accordance with such continuous deformation of the diaphragm 12, the discharge liquid accumulated in the nozzle 8 part and the reservoir 14 flows into the pressure chamber 13. Then, when the applied voltage between the cavity substrate 2 and the individual electrode 18 is removed, the suction force is lost, and the diaphragm 12 returns to the original state. In contrast to the case where the diaphragm 12 comes into contact with the individual electrode 18, the return mode of the diaphragm 12 proceeds sequentially from the center portion toward both ends and the middle portion of the diaphragm 12 in the longitudinal direction. As a result, the pressure inside the pressure chamber 13 increases and ink is ejected from the nozzles 8.

The electrostatic force generated between the diaphragm 12 and the individual electrode 18 increases in inverse proportion to the square of the distance between the diaphragm 12 and the individual electrode 18 (corresponding to the gap 20). Therefore, as shown in FIG. 3, the diaphragm 12 sequentially contacts the individual electrode 18 from the individual electrodes 182, 187, 192 in the narrow part of the gap 20, and finally the individual electrode 184 in the center part having the widest gap 20. , 190 abuts. At that time, the ink in the pressure chamber 13 moves in the direction of the arrow shown in FIG. 3 according to the operation of the diaphragm 12.
In this inkjet head 1, the width of the gap 20 between the intermediate portion and both end portions (the nozzle 8 communication side and the reservoir 14 communication side) in the longitudinal direction of the pressure chamber 13 is the narrowest, and from there, between the intermediate portion and the both end portions. The width of the gap 20 is widened toward the center portion. Therefore, the ink in the pressure chamber 13 moves from the nozzle 8 side and the reservoir 14 side toward the center due to the expansion of the pressure chamber 13 due to the contact of the diaphragm 12 with the individual electrode 18, and at the center of the pressure chamber 13. The ink also moves toward the nozzle 8 side and the reservoir 14 side, respectively. Thereafter, when the potentials of the diaphragm 12 and the individual electrode 18 are set to the same potential, and the electric charges in those portions are discharged, the diaphragm 12 is separated from the individual electrode 18 in order from the widest portion to the narrowest portion of the gap 20. Leave sequentially. As a result, the ink in the pressure chamber 13 moves and vibrates in the direction opposite to the arrow in the drawing, and ink is ejected from the nozzle 8 due to the pressure fluctuation. After the ink is ejected, the ink in the pressure chamber 13 is stabilized by the ink supplied from the reservoir 14 via the orifice 15 by the restoring force of the meniscus while the residual vibration is attenuated.

  FIG. 4 is a diagram for explaining the behavior of ink in the pressure chamber 13 in the above-described ink jet head 1, and is a diagram relating to explanation of parameters of the ink flow path, particularly inertance which is a mass component. The inertance in the pressure chamber 13 is determined by the channel cross-sectional area in the pressure chamber 13, the channel length, and the ink density. Here, the pressure chamber 13 is divided into (1) the nozzle 8 communication side to the portion corresponding to the deepest portion 184 of the individual electrode 18 and (2) the portion corresponding to the deepest portion 184 of the individual electrode 18 to the longitudinal direction of the pressure chamber 13. An intermediate part, (3) an intermediate part in the longitudinal direction of the pressure chamber 13 to a part corresponding to the deepest part 190 of the individual electrode 18, and (4) a part corresponding to the deepest part 190 of the individual electrode 18 to the reservoir 14 communication side. Consider it divided into four parts.

According to the change of the diaphragm 12 due to the suction force, the ink of each part moves in the direction of the arrow shown in FIG. 3, and the dynamic resistance (acceleration) of the ink as the fluid at that time is the inertance M1 of each part. , M2, M3, M4.
Ink vibration on the nozzle 8 side of the pressure chamber 13 that contributes most to ink ejection is determined by M1 and other inertances. At this time, inertance Mn1 that contributes as a load to the electrostatic actuator including the diaphragm 12 and the individual electrode 18 is expressed by the following equation.
Mn1 = {1 / M1 + 1 / (M2 + M3 + M4)} ^-1
The electrode forming groove 19 of the electrode substrate 3 is set with the depth determined so that each inertance is M = M1 = M2 = M3 = M4. Therefore, Mn1 has the following value after all. .
Mn1 = 3/4 ・ M

On the other hand, in the case of the conventional configuration in which the width of the gap 20 in the longitudinal direction of the pressure chamber 13 is constant, the inertance Mn is expressed by the following equation.
Mn = {1 / (M1 + M2) + 1 / (M3 + M4)} ^-1
Also in the conventional example, the position of the deepest part is determined and set with respect to the gap 20 between the diaphragm 12 and the individual electrode 18 with respect to the same pressure chamber 13 so that 2M = M1 + M2 = M3 + M4. In this case, Mn is the following value.
Mn = M
However, there are two main ink flows in the pressure chamber 13 at this time: the nozzle 8 communication side with inertance M1 + M2 and the reservoir 14 communication side (orifice 15 side) with M3 + M4.

That is, the inertance Mn1 that contributes to the electrostatic actuator of the present embodiment as a load is compared to the conventional value Mn.
Mn1 = 3/4 ・ Mn
It becomes. Therefore, the gap formed by the diaphragm 12 and the individual electrode 18 on the bottom surface of the pressure chamber 13 as in the present invention, rather than the electrostatic actuator of the type that drives the entire flow path at a time as shown in the conventional example. 20 is formed so as to have stepped steps on the left side and the right side of the pressure chamber 13 in the middle in the longitudinal direction, so that the ink drive using the diaphragm 12 can be performed with a smaller dynamic load. It can be understood that, if the same ink volume (excluded volume) is used, faster driving and lower voltage driving are possible.

  Further, since the ink jet head 1 has a small ink driving dynamic load, the response of the meniscus pull-in at the time of suction of the diaphragm 12 is enhanced. A large displacement and a larger vibration amplitude of ink in the pressure chamber 13 can be generated, and as a result, the amount of ink discharged from the nozzle 8 can be controlled. The ink discharge amount is controlled by controlling the charging speed with high drive responsiveness. For example, it is possible to eject a large amount of ink by sucking the diaphragm 12 at a high speed by rapid charging and discharging minute ink, and by gently sucking the diaphragm 12 by a slow charge.

  As described above, according to the inkjet head 1, the load when the diaphragm 12 contacts the individual electrode 18 can be reduced, and the diaphragm 12 can be quickly sucked into the individual electrode 18. The discharge capacity of the head can be improved by increasing the ink discharge amount without causing voltage or damaging the responsiveness. As a result, it is possible to increase the speed and performance of a printing apparatus using this. In addition, it can be easily realized without requiring extra wiring or complicated control for realizing these driving operations.

  By the way, it is preferable that the stepped adjacent steps of the individual electrode 18 are gradually reduced toward the central portion between the intermediate portion and both end portions in the longitudinal direction of the pressure chamber 13. . By doing so, the vibration plate 12 can be continuously and smoothly abutted from the middle portion and both end portions in the longitudinal direction of the pressure chamber 13 toward the central portion between them, and therefore the behavior of the ink. This is because the control regarding the discharge becomes easier.

  Further, the maximum distance of the gap 20 between the intermediate portion in the longitudinal direction of the pressure chamber 13 and the longitudinal end portion on the nozzle 8 communication side is defined as the gap between the intermediate portion and the longitudinal end portion on the reservoir 14 communication side. It is preferable that the distance is larger than the maximum distance of 20. In this way, since the amount of deformation of the diaphragm 12 on the nozzle 8 side of the pressure chamber 13 can be made large, it becomes easier to perform drive control in accordance with the ink meniscus drawing of the nozzle 8 portion. is there.

  As shown in FIG. 5, the electrode forming groove 19 of the electrode substrate 3 is not formed in a step shape as in the previous examples, but is formed on a continuous inclined surface, and an individual electrode having a uniform thickness is formed there. When 18 is formed, the change of the diaphragm 12 due to the suction force is performed more smoothly, so that it is possible to further control the ink behavior and the ejection amount.

Next, an example of the method for manufacturing the inkjet head 1 shown in the first embodiment will be briefly described with reference to FIGS. In the following description, each member and each element will be described with reference numerals used so far.
FIG. 7 is a flowchart showing an example of the manufacturing process of the electrode substrate 3. The electrode substrate 3 is formed by sputtering chromium as a protective film against wet etching on a glass substrate such as borosilicate glass (also denoted by reference numeral 3) (S1). Next, patterning is performed so that the electrode forming groove 19 can be formed using photolithography or the like, and chromium in a predetermined portion is removed (S2). Thereafter, the glass substrate 3 is wet-etched to form an electrode forming groove 19 in the chromium removal portion (S3). In the steps S2 to S3, as shown in FIGS. 6A to 6G, the removal of the predetermined portion 32 of the chromium 31 on the glass substrate 3 and the etching of the electrode forming groove 19 are performed a plurality of times. By repeating, it is possible to form the electrode forming groove 19 having a multi-step shape.
In FIG. 6, only a part of the electrode forming groove 19 shown in FIG. 2 is shown, but the electrode forming groove 19 is provided between the middle portion and both end portions of the pressure chamber 13 in the longitudinal direction. Can be formed by simultaneous processing.

Subsequently, after removing and removing chromium (S4), an ITO film to be an individual electrode later is formed on the entire surface of the glass substrate 3 on which the electrode forming groove 19 is formed by sputtering (S5). Further, the ITO of the glass substrate 3 is patterned to leave only the individual electrodes 18 (including lead portions and electrode terminal portions) in the electrode forming groove 19 and remove the remaining ITO (S6). Finally, a glass hole to be the ink supply port 17B is processed (S7), and the electrode substrate 3 is completed (S8).
In addition, the electrode substrate of the inkjet head shown in FIG. 5 is used for the removal of the predetermined portion 32 of the chromium 31 and the electrode formation as shown in (a) to (g) of FIG. By repeating the etching of the groove 19 many times, it is possible to form the concave electrode forming groove 19 having a step but approximating a curved surface.

FIG. 8 is a flowchart showing an example of the manufacturing process of the cavity substrate 2. First, boron diffusion treatment for doping boron is performed on one side of a silicon substrate (also denoted by reference numeral 2) (S11). Subsequently, the silicon substrate 2 is heat-treated to form a SiO ₂ thermal oxide film on both sides (S12). This thermal oxide film serves as a hard mask when the silicon substrate 2 is etched. Subsequently, the thermal oxide film is patterned to remove a portion of the thermal oxide film that becomes the pressure chamber 13, the reservoir 14, and the like (S13). Thereafter, the silicon substrate 2 is etched with a KOH solution to form a concave portion that becomes the pressure chamber 13, the reservoir 14, and the like (S14). In this case, in the portion doped with boron, the boron doped layer acts as an etching stop layer, and the etching with the KOH liquid stops. Therefore, the boron doped layer becomes the bottom wall of the pressure chamber 13, that is, the diaphragm 12. Finally, after removing the thermal oxide film remaining on the silicon substrate 2 once, a thermal oxide film (or TEOS oxide film) is formed again on both sides of the silicon substrate 2 (S15). The oxide film acts as an ink protective film on the pressure chamber 13 and reservoir 14 side, and acts as an insulating film on the opposite side. Thus, the cavity substrate 2 in which the cavities forming the ink flow path are formed is completed (S16).

FIG. 9 is a flowchart showing an example of the assembly process of the inkjet head. The electrode substrate 3 manufactured as shown in FIG. 7 and the cavity substrate 2 manufactured as shown in FIG. 8 are laminated by anodic bonding or the like (S21). And the clearance gap 20 between the separate electrode 18 and the diaphragm 12 formed by those lamination | stacking is sealed with the sealing material 22 (S22). Thereafter, the nozzle substrate 4 is bonded and bonded to the cavity substrate 2 (S23). Further, the laminated substrate composed of the cavity substrate 2, the electrode substrate 3 and the nozzle substrate 4 manufactured in units of silicon wafers is cut into predetermined units (S24). Thereafter, a terminal (FPC) with a cable is attached to the electrode terminal portion 18A of the electrode substrate 3 and the common electrode terminal 21 of the cavity substrate 2 (S25), thereby completing the basic shape of the inkjet head 1 (S26).
It should be noted that the electrode substrate 3 formed as shown in FIG. 7 is anodically bonded to the silicon substrate 2 before the cavity is formed, and then the cavity substrate 2 is subjected to processing for forming a cavity in the silicon substrate 2 according to FIG. The inkjet head 1 may be manufactured by bonding the nozzle substrate 4 to the laminate of the electrode substrate 3 and the electrode substrate 3.

Embodiment 2
FIG. 10 shows an ink jet printer according to a second embodiment provided with an ink jet head 1 which is a droplet discharge head according to the present invention. As described above, since the inkjet head 1 can reduce the drive voltage and sufficiently discharge the droplets, the printer 100 using the inkjet head 1 can increase the ink discharge amount with low power consumption. In addition, since the driving speed of the diaphragm 12 is increased, the printing speed is also increased. Therefore, the printer 100 has excellent printing performance.
In addition to ejecting ink, the liquid droplet ejection head of the present invention is not limited to various liquids or solutions, for example, a solution containing a filter material for a color filter, a solution containing a light emitting material for an organic EL display device, It can also be used as a discharge device for various droplets such as a solution containing a wiring material and a biological liquid.

1 is an exploded perspective view showing an inkjet head according to Embodiment 1 of the present invention. FIG. 2 is a longitudinal sectional view along the pressure chamber longitudinal direction of the ink jet head of FIG. 1. The figure corresponding to FIG. 2 explaining operation | movement of an inkjet head. The figure regarding description of the inertance of the pressure chamber of an inkjet head. FIG. 5 is a view corresponding to FIG. 2 illustrating a modification of the ink jet head according to the first embodiment. Explanatory drawing of the manufacturing process of the groove | channel for electrode formation of an electrode substrate. The flowchart which shows an example of the manufacturing process of an electrode substrate. The flowchart which shows an example of the manufacturing process of a cavity board | substrate. 5 is a flowchart showing an example of an assembly process of an inkjet head. FIG. 5 is a perspective view showing an ink jet printer according to Embodiment 2 of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Inkjet head, 2 Cavity substrate, 3 Electrode substrate, 4 Nozzle substrate, 6 1st nozzle hole, 7 2nd nozzle hole, 8 Nozzle, 12 Diaphragm, 13 Pressure chamber, 14 Reservoir, 15 Orifice, 17A, 17B Ink supply port, 18 individual electrode, 18A electrode terminal portion, 19 electrode forming groove, 20 gap, 21 common electrode terminal, 22 sealing material, 25 drive circuit, 100 printer, 181 to 193 Individual electrode of each stepped portion.

Claims (7)

A nozzle substrate having a nozzle;
The bottom surface has a pressure chamber formed in an oblong diaphragm that can be deformed by electrostatic force, one end side in the longitudinal direction of the pressure chamber communicates with the nozzle of the nozzle substrate, and the other end side in the longitudinal direction is A cavity substrate in communication with a reservoir for storing the discharge liquid;
An electrode substrate having an individual electrode, wherein the individual electrode is disposed to face the diaphragm with a gap,
The gap between the diaphragm and the individual electrode is gradually widened between the middle portion and both end portions in the longitudinal direction of the pressure chamber as it goes to the central portion between them. Droplet discharge head.   Of the gap, the gap width of the portion corresponding to the position where the inertance of the discharge liquid in the pressure chamber becomes equal on the nozzle communication side and the reservoir communication side of the pressure chamber, and both end portions in the longitudinal direction of the pressure chamber The liquid droplet ejection head according to claim 1, wherein the gap width of the liquid crystal is narrowest.   2. The droplet discharge according to claim 1, wherein, among the gaps, a gap width at a middle portion in the longitudinal direction of the pressure chamber and a gap width at both end portions in the longitudinal direction of the pressure chamber are the narrowest. head.   The maximum distance of the gap between the longitudinal intermediate portion of the pressure chamber and the longitudinal end portion on the nozzle communication side is the maximum distance between the intermediate portion and the longitudinal end portion on the reservoir communication side. The droplet discharge head according to claim 1, wherein the droplet discharge head is larger than a maximum distance of the gap.   5. The droplet discharge head according to claim 1, wherein the individual electrodes of the electrode substrate are formed with steps in a stepped manner corresponding to the gaps.   The stepwise adjacent steps of the individual electrodes are smaller between the middle portion and both end portions in the longitudinal direction of the pressure chamber as they go to the central portion between them. Item 6. The droplet discharge head according to Item 5.   A droplet discharge apparatus comprising the droplet discharge head according to claim 1 in a droplet discharge portion.

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